1. Field of the Invention
The present invention relates to a liquid crystal display device.
2. Description of the Related Art
Japanese Patent Application Laid-open No. 2007-286627 discloses a liquid crystal display device including a direct type backlight unit. In the liquid crystal display device, a plurality of light emitting diodes are used as light sources of the backlight unit. The light emitting diodes are disposed in matrix across an entire region of the backlight unit.
In the liquid crystal display device described in Japanese Patent Application Laid-open No. 2007-286627, the light emitting diodes are disposed across the entire region of the backlight unit, and hence the size of a substrate on which a large number of light emitting diodes are disposed needs to be large enough to cover the entire region of the backlight unit. This increases cost for preparing a large number of light emitting diodes as well as a material cost of the substrate on which the light emitting diodes are to be disposed.
To address the problem, it is conceivable to dispose the light emitting diodes in a concentrated manner in a part of the backlight unit, for example, in the vicinity of the center of the backlight unit in the short side direction, along the long side direction of the backlight unit so that light beams emitted from the light emitting diodes are reflected or diffused so as to irradiate an entire image formation region of the rear surface of the liquid crystal panel with light beams.
There are various methods of reflecting or diffusing light beams emitted from the light emitting diodes. However, in a method using a light guide plate or a method using a plane lens such as a Fresnel lens, manufacturing cost of the light guide plate or the Fresnel lens is high and the weight increases as well. Therefore, the applicant of the present invention has studied a method of reflecting/diffusing light beams with the use of a reflection sheet which is curved so as to have a concave front surface, that is, a concave surface facing the liquid crystal panel. According to this method, the manufacturing cost can be suppressed and the weight can be reduced.
However, for example, in the case where the liquid crystal display device is used for a large-size television set, the size of the liquid crystal panel also increases, and hence the reflection sheet is warped, and it is difficult to irradiate the entire image formation region of the rear surface of the liquid crystal panel with light beams uniformly.